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Open access

Reinhard Nolz and Marek Rodný

Abstract

Employing evapotranspiration models is a widely used method to estimate reference evapotranspiration (ETREF) based on weather data. Evaluating such models considering site-specific boundary conditions is recommended to interpret ETREF-calculations in a realistic and substantiated manner. Therefore, we evaluated the ASCE standardized ETREF-equations at a subhumid site in northeastern Austria. We calculated ETREF-values for hourly and daily time steps, whereof the former were processed to sum-of-hourly values. The obtained data were compared to each other and to ET-values measured by a weighing lysimeter under reference conditions. The resulting datasets covered daily data of the years 2004 to 2011.

Sum-of-hourly values correlated well (r2 = 0.978) with daily values, but an RMSE of 0.27 mm specified the differences between the calculation procedures. Comparing the calculations to lysimeter measurements revealed overestimation of small ETREF-values and underestimation of large values. The sum-of-hourly values outperformed the daily values, as r2 of the former was slightly larger and RMSE was slightly smaller. Hence, sum-of-hourly computations delivered the best estimation of ETREF for a single day. Seasonal effects were obvious, with computations and measurements being closest to each other in the summer months.

Open access

Shengqi Jian, Zening Wu and Caihong Hu

Abstract

Tree transpiration plays a determining role in the water balance of forest stands and in seepage water yields from forested catchments, especially in arid and semiarid regions where climatic conditions are dry with severe water shortage, forestry development is limited by water availability. To clarify the response of water use to climatic conditions, sap flow was monitored by heat pulse velocity method from May to September, 2014, in a 40–year–old Pinus tabulaeformis Carr. plantation forest stands in the semiarid Loess Plateau region of Northwest China. We extrapolated the measurements of water use by individual plants to determine the area–averaged transpiration of the woodlands. The method used for the extrapolation assumes that the transpiration of a tree was proportional to its sapwood area. Stand transpiration was mainly controlled by photosynthetically active radiation and vapor pressure deficit, whereas soil moisture had more influence on monthly change in stand transpiration. The mean sap flow rates for individual P. tabulaeformis trees ranged from 9 to 54 L d−1. During the study period, the mean daily stand transpiration was 1.9 mm day−1 (maximum 2.9 and minimum 0.8 mm day−1) and total stand transpiration from May to September was 294.1 mm, representing 76% of the incoming precipitation over this period. Similar results were found when comparing transpiration estimated with sap flow measurements to the Penman–Monteith method (relative error: 16%), indicating that the scaling procedure can be used to provide reliable estimates of stand transpiration. These results suggested that P. tabulaeformis is highly effective at utilizing scarce water resources in semiarid environments.

Open access

Amira A. Rashad, Sara Nageeb El-Helaly, Randa T. Abd El Rehim and Omaima N. El-Gazayerly

Abstract

Reduced bioavailability of azelnidipine is related to its poor aqueous solubility and extensive first-pass metabolism, which hinder its efficacy. These problems were addressed by implementing (1) a liquisol technique for promoting the dissolution rate in a controlled-release manner and (2) a core-in-cup bucco-adhesive drug delivery system as an alternative to the oral route. A 33 factorial design was used to study the effects of polymer type (sodium carboxymethyl cellulose (CMC Na), chitosan, or Carbomer P940) concentration (5, 10 or 15 %) and preparation technique (simple mix, liquisol or wet granulation) on the dissolution and mucoadhesion of core-in-cup azelnidipine buccoadhesive tablets. Tablet micromeritics, swelling index, mucoadhesive strength and in vitro release were characterized. Statistical analyses of these factors show ed significant effects on the studied responses, where F#16 prepared by the liquisol technique and containing 15 % CMC Na was chosen with an overall desirability of 0.953.

Open access

Marcin Gackowski, Marcin Koba, Katarzyna Mądra-Gackowska and Stefan Kruszewski

Abstract

New methods for assaying trimetazidine dihydrochloride on the basis of thin layer chromatography and spectrophotometry are proposed and compared in the paper. In HPTLC/UV-densitometry, separation is achieved by using a mobile phase composed of ammonia-methanol (30:70, V/V) on silica gel HPTLC plates F254. Quantification using a non-linear calibration curve is accomplished by densito-metric detection at 230 nm. Derivative spectrophotometric determination of trimetazidine dihydrochloride is carried out from the fourth derivative of the absorbance at 233 nm in peak-zero mode. Statistical comparison led to the conclusion that there is no significant difference between the two studied methods and, moreover, that they demonstrate satisfactory accuracy and precision for routine applications.

Open access

Jakub Vysloužil, Kateřina Kubová, Veronika Nováková Tkadlečková and David Vetchý

Abstract

The original purpose of vaginally applied microbicides was to slow down the HIV epidemic among the population until an effective vaccination was developed. Nowadays, antiretrovirals applied in the form of gels or vaginal rings are considered most prominent in this field and are tested via vaginal or, rarely, rectal applications in numerous clinical studies (9 different antiretroviral drugs in 33 clinical studies, especially in Africa). Only tenofovir (1 % gel) and dapivirine (25 mg in vaginal ring) progressed into the phase III clinical testing. Their efficiency depended on the user´s strict adherence to the application regimen (for tenofovir 54 %, for dapivirine 61 % in participants over 25 years of age). Despite this, they are expected to be important and effective tools of preventive medicine in the near future. This review summarizes the results obtained during long-term clinical testing (2005–2018) of antiretroviral drugs against vaginal and rectal transmission of HIV infection.

Open access

Aleksandra Kapedanovska Nestorovska, Krume Jakjovski, Zorica Naumovska, Zoran Sterjev, Nadica Matevska Geskovska, Kristina Mladenovska, Ljubica Suturkova and Aleksandar Dimovski

Abstract

The relative contribution of CYP2C9 allelic variants to the pharmacokinetics (PK) of ibuprofen (IBP) enantiomers has been studied extensively, but the potential clinical benefit of pharmacogenetically guided IBP treatment is not evident yet. The role of AKR1D1*36C>T (rs 1872930) allelic variant in interindividual variability of CYP450 mediated drug metabolism was recently elucidated. A total of 27 healthy male subjects, volunteers in IBP single-dose two-way cross-over bioequivalence studies were genotyped for CYP2C9*2, CYP2C9*3 and AKR1D1*36 polymorphisms. The correlation between CYP2C9 and AKR1D1 genetic profile and the PK parameters for S-(+) and R-(−)-IBP was evaluated. Remarkable changes in the PK values pointing to reduced CYP2C9 enzyme activity were detected only in the CYP2C9*2 allelic variant carriers. Statistically significant association between the AKR1D1*36 allele and the increased IBP metabolism (low AUC 0-t and 0–∞, high Cl tot and short t max values for both enantiomers) was observed in subjects carrying the CYP2C9 *1/*3 or CYP2C9*1/*1 genotype. The clinical value of concomitant CYP2C9 and AKR1D1 genotyping has to be further verified.

Open access

Ludmila Vīksna, Mārtiņš Vilcāns, Indra Zeltiņa, Aija Leidere-Reine, Angelika Krūmiņa, Oksana Koļesova, Jeļena Ļeviņa and Aleksandrs Koļesovs

Abstract

Health care personnel (HCP) are at high risk of acquiring influenza due to exposure to patients. However, vaccination in HCP is lower than 40% for most European countries. The aim of this study was to determine the attitude towards influenza vaccination and possible reasons for this attitude in HCP. A cross-sectional study was performed in a multidisciplinary hospital of Latvia. The sample (n = 1099) included doctors (239), nurses (418), care services (236), administrative staff (108), and technical support staff (98). Five questions addressed vaccination of planned patients and HCP, knowledge of etiological anti-influenza drugs, and their storage at the hospital for immediate use. The results revealed that the level of regular vaccination against influenza in HCP was relatively low (14%). This contrasted with a more positive attitude towards vaccination of patients (53%) and personnel (60%). This contrast provided evidence for a low level of proactive action. High expectations regarding medications covered by the hospital (82%) indicated transferring of part of personal responsibility to the organisation. Doctors demonstrated a better understanding of the problem and a higher level of vaccination. However, some of doctors’ attitudes showed underestimation of influenza-associated risk.